Sustained effects of prior red light on pupil diameter and vigilance during subsequent darkness

Wisse P van der Meijden, Bart H W Te Lindert, Jennifer R Ramautar, Yishul Wei, Joris E Coppens, M. Kamermans, Christian Cajochen, Patrice Bourgin, Eus J W Van Someren

Research output: Contribution to journal/periodicalArticleScientificpeer-review

12 Citations (Scopus)


Environmental light can exert potent effects on physiology and behaviour, including pupil size, vigilance and sleep. Previous work showed that these non-image forming effects can last long beyond discontinuation of short-wavelength light exposure. The possible functional effects after switching off long-wavelength light, however, have been insufficiently characterized. In a series of controlled experiments in healthy adult volunteers, we evaluated the effects of five minutes of intense red light on physiology and performance during subsequent darkness. As compared to prior darkness, prior red light induced a subsequent sustained pupil dilation. Prior red light also increased subsequent heart rate and heart rate variability when subjects were asked to perform a sustained vigilance task during the dark exposure. While these changes suggest an increase in the mental effort required for the task, it could not prevent a post-red slowing of response speed. The suggestion that exposure to intense red light affects vigilance during subsequent darkness, was confirmed in a controlled polysomnographic study that indeed showed a post-red facilitation of sleep onset. Our findings suggest the possibility of using red light as a nightcap.

Original languageEnglish
Article number20180989
JournalProceedings of the Royal Society B-Biological Sciences
Issue number1883
Publication statusPublished - Jun 2018


  • Journal Article


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